Recently, in a manufacturing process of semiconductor devices, for example, an increase in diameter and decrease in thickness of semiconductor substrates, such as silicon wafers, compound semiconductor wafers or the like, are in progress. A plurality of electronic circuits is formed on a semiconductor substrate, which will be hereinafter referred to as a target substrate. When transferring or polishing a large and thin target substrate, it is likely that the target substrate is bent or broken. For this reason, a target substrate is reinforced by bonding a support substrate thereto, the reinforced target substrate is transferred or polished, and then the support substrate is peeled off from the target substrate.
For example, there is known a peeling method. In this method, a support substrate is sucked and held by a first holding unit. A target substrate is sucked and held by a second holding unit. Under this state, the support substrate is peeled off from the target substrate from one end portion of the support substrate toward the other end portion thereof by moving the outer periphery portion of the first holding unit away from the second holding unit, namely by moving the outer periphery portion of the first holding unit vertically upward, through the use of a moving unit.
In the aforementioned method, for example, as shown in FIG. 26, a moving unit 700 includes a support member 701 and a moving mechanism 702. The moving mechanism 702 is fixed to a base portion 710. Furthermore, a first holding unit 720 for holding a support substrate S includes an elastic member 721 and a plurality of sucking parts 722. The support member 701 is connected to the outer periphery portion of the elastic member 721.
When peeling off the support substrate S from the target substrate W, if the first holding unit 720 is pulled upward by the moving unit 700, the elastic member 721 of the first holding unit 720 is flexibly deformed along with the pulling operation due to elasticity of the elastic member 721. At this time, the moving mechanism 702 is kept fixed to the base portion 710. Therefore, as shown in FIG. 27, the position of one end portion S1 of the support substrate S in the horizontal direction (the X-axis direction in FIG. 27) remains unchanged. As a result, the support substrate S is stretched just as much as the vertical upward displacement of one end portion S1 of the support substrate S. Thus, a force F acting toward one end portion S1 (acting in the X-axis negative direction in FIG. 27) is generated in the peeling-off portion where the support substrate S is peeled off from the target substrate W. It is likely that the target substrate W or the support substrate S is damaged by the force F. Specifically, according to the studies conducted by the present inventors, it was found that, if the diameter of the support substrate S (or the target substrate W) is, e.g., 300 mm, and if the height H of one end portion S1 of the support substrate S moved vertically upward is 20 mm, the target substrate W or the support substrate S is likely to be damaged.
This problem may be generated in a manufacturing process of an SOI (Silicon On Insulator) or the like which involves peeling-off of substrates.